"Improved" means to obtain or manipulate fatty acid compositions, from biosynthetic or natural plant sources, are needed. For example, novel oil products, improved sources of synthetic triacylglycerols (triglycerides), alternative sources of commercial oils, especially tropical oils (i.e., palm kernel and coconut oils), and plant oils found in trace amounts from natural sources are desired for a variety of industrial and food uses.
To this end, the Fatty Acid Synthesis (FAS) system in plants and bacteria, FAS-II, has been studied. The mechanism of producing "long-chain fatty acids", i.e., fatty acids having a carbon chain length of equal to or greater than 16 carbon atoms (C16), via the acyl carrier protein (ACP)-dependent, plastid-localized FAS system of plants is relatively well characterized. However, the amino acid and corresponding nucleic acid sequences of many of the proteins responsible for this activity have not been determined. In particular, the enzyme by which free long-chain fatty acids are produced has been studied in several different crops. Nevertheless, the mechanism(s) by which plants produce fatty acids having shorter carbon chains, i.e., less than C16 atoms, including short-chain free fatty acids (C4-C8) and medium-chain free fatty acids (C8-C14), has remained elusive.
Characterization of thioesterases (also known as hydrolases) would be useful for the further study of plant FAS systems and for the development of novel and/or alternative oils sources. Generating a spread of C4, C6 and C8 short chain 3-keto fatty acids could become a key improvement in polyhydroxybutyrate (PHB)-based biodegradable plastics made in bacteria and plants. Medium-chain fatty acids have special importance in the detergent and lubricant industries or in the formulation of edible oils with reduced caloric value or other health benefits. See for example, U.S. Pat. No. 4,863,753 and Barch, A. C. & Babayan, V. K., Am. J. Clin. Nat. (1982) 36:950-962. Longer chain fatty acids may have certain other utilities, i.e., C16 and C18 have particular uses in margarine and other solid oil-based products and very long chain fatty acids also have specialized uses, i.e., C22 is used to make peanut butter smoother. As such, a ready source of a variety of fatty acid lengths, including storage lipids which have incorporated differing chain length fatty acids in desired ratios, are desired for a variety of industrial and food use fields. As the biosynthetic pathway for chain termination of fatty acids in plants is determined, the system can be adapted for application in vivo and in vitro.
Thus, studies of plant chain termination mechanisms may provide means to further enhance, control, modify or otherwise alter the length of fatty acid products or resulting triglycerides and oils. And, the elucidation of the factor(s) critical to the natural production of free fatty acids in plants is desired, including the purification of such factors and the characterization of element(s) and/or co-factors which enhance the efficiency of the system. Of special interest are the nucleic acid sequences of genes encoding factors related to the production of such free fatty acids for applications in genetic engineering.